A polylactic acid resin is inexpensive because L-lactic acid used as a raw material is produced by a fermentation method using a sugar extracted from maize, potatoes, or the like. Also, the polylactic acid resin has a very low amount of a carbon dioxide discharge because the raw material is plant-derived, and the properties of the resin include strong rigidity and high transparency. Therefore, the utilization of polylactic acid resins is expected to be promising at present.
However, the polylactic acid resin has a slow crystallization velocity, so that if crystallization is carried out, a long time period is required, thereby worsening the productivity. In view of the above, a technique of improving a crystallization rate by blending a crystal nucleating agent or the like in the polylactic acid resin has become known.
For example, in Patent Publication 1, a polylactic acid resin composition having an excellent crystallization velocity is obtained by blending a polylactic acid resin with a phenylphosphonic (acid) derivative having a particular structure.
In Patent Publication 2, a polylactic acid resin composition having an excellent crystallization velocity and heat resistance is obtained by blending a biodegradable resin with a mixture of at least one compound selected from the compounds having a hydroxyl group and an amide group in the molecule and a metal salt of a phenylphosphonic acid.
In Patent Publication 3, a polylactic acid resin composition having an excellent crystallization velocity and heat resistance is obtained by blending a polylactic acid resin with a particular polyester-polyol and a crystal nucleating agent, and a polylactic acid resin composition having even higher heat resistance is obtained by previously mixing the polyester-polyol and the crystal nucleating agent upon melt-kneading, thereby forming the crystal nucleating agent into fine particles.
In addition, Patent Publication 4 discloses a method utilizing an aliphatic phosphoric ester compound having an aliphatic chain having 12 to 28 carbon atoms or the like, as a lubricant during molding of a polylactic acid-based resin composition. Patent Publication 5 discloses that a secondary workability such as stretch workability can be improved in the production of a porous sheet by adding several aliphatic phosphoric triesters as plasticizers together with a crystal nucleating agent.